It is known that iron bound nitric oxide and S-nitrosothiols in blood samples degrade and liberate free nitric oxide when the samples are irradiated with ultraviolet (UV) electromagnetic radiation, allowing detection of amount of free nitric oxide.
In existing machines for detecting amount of nitric oxide bound to hemoglobin and in nitrosothiols in blood, a 150 W mercury vapor lamp is used as a high intensity, broad spectrum UV source that irradiates liquid blood-containing samples as they flow through a Pyrex® glass coil. The use of a 150 W mercury vapor lamp requires a large surface area sample. A flow-through process is necessary to provide the large surface area. A flow-through stream is aerated with a helium carrier gas stream, allowing free nitric oxide gas to be transported to a separate unit that houses a nitric oxide detector where the freed nitric oxide is reacted with ozone to generate light (chemiluminescence) which is detected by a photomultiplier tube. This method is described in Stamler et al. U.S. Pat. No. 5,459,076 and in Stamler U.S. Pat. No. 5,891,735. This method while useful in a research setting is too cumbersome for a clinical setting. The narrow diameter of the tubing through which the samples pass and elevated temperatures encountered, prohibit measurement on turbid samples in the glass coil of the tubing. Furthermore, the glass coil needs to be reused, requiring cleaning between runs.
Lucht et al. U.S. Pat. No. 6,982,426 teaches a nitric oxide sensor and method comprising passing a signal beam from a laser in a crystal through a sample into a photomultiplier tube and detection of output ultraviolet radiation which indicates level of nitric oxide by comparison with control based on nitric oxide absorption of ultraviolet radiation. Measurements are made by photomultiplier tubes. The apparatus and method are not useful for biological samples and lack sensitivity.
Sackner et al. U.S. Pat. No. 7,090,648 teaches light/laser therapy in wound healing and indicates this therapy releases nitric oxide from hemoglobin and states that this has the potential to enhance wound healing.